1. Field of the Invention
The present invention relates to a light emitting device which has an element with a luminescent material put between electrodes, a manufacturing method thereof, and an electronic appliance using the light emitting device for the display (an indication display or a displaying monitor), particularly to a light emitting device using a luminescent material by which EL (Electro Luminescence) can be obtained (hereinafter referred to as an EL material) and a manufacturing method thereof. The light emitting device according to the present invention includes an organic EL display and an OLED (Organic Light Emitting Diode).
The luminescent material that can be used in the present invention includes all of materials which emit light (phosphorescence and/or fluorescence) through singlet excitation, triplet excitation, or both.
2. Description of the Related Art
Recently, there has been proceeding development of light emitting devices (hereinafter referred to as EL light emitting devices) using self-light emitting elements (hereinafter referred to as EL elements) to which EL phenomenon of luminescent materials is applied. The EL light emitting devices, being display devices using self-light emitting elements, necessitate no back-lighting as in liquid crystal display devices. Furthermore, with their wide viewing angles, the EL light emitting devices attract attention for being used as displays of portable units used outdoors.
There are two types of the EL light emitting device, i.e. an active matrix type and a passive matrix type. There has been development of both types actively carried out. At present, the active matrix type EL light emitting device is particularly noted. The active matrix type EL light emitting device is characterized in that a thin film transistor (hereinafter referred to as TFT) is provided for each of pixels of a pixel section to control an amount of current flowing in an EL element.
The advantage of the active matrix type is that a highly fine image can be displayed and an image with larger amount of information can be provided.
However, it makes a manufacturing process complicated to provide the TFT for each of the pixels, and there are caused problems of reduction in yield and increase in manufacturing cost due to a protracted manufacturing term. In particular, many photolithography steps cause remarkable reduction in yield, and reduction in number of photolithography steps was an important subject.